| 1. |
- Mukerji, Joydeb, et al.
(författare)
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Wear of Nitrogen Ceramics and Composites in contact with Bearing Steel under Oscillating Sliding Conditions
- 1998
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Ingår i: Ceramics International. - 0272-8842 .- 1873-3956. ; 24:1, s. 19-24
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Tidskriftsartikel (refereegranskat)abstract
- The wear of nitrogen based ceramics in contact with bearing steel balls (SAE 52100) was investigated under reciprocating sliding conditions at a velocity of 0.1 m/s, and 20 N, 40 N and 100 N load. Three types of ceramics were studied: viz. hot pressed silicon nitride (HPSN) sintered with selected liquid in the system yttria-aluminium nitride-silica and composites of HPSN with BN and TiC; SiAlON formulated with different amounts of alumina and silica; and aluminatitanium nitride composite having 60 mol% TiN. Among the HPSN composites, HPSN 15vol% TiC had the lowest average wear factor (K) of 2.0 × 10- 5mm3/m/ N. The SiAlONs, in general, had the highest K and this increased with increasing O concentration. The lowest K value for SiAlON ceramic was 6.9 × 10-5mm3/m/N. The high K value of SiAlON is attributed to O substitution, which promotes adhesive wear resulting in mutual material transfer. The lowest wear of all the ceramics tested was found for the alumina-titanium nitride composite, the wear factor being of the order of 4.4 × 10-7mm3/m/N, which is one order of magnitude lower than the other nitrogen ceramics. In the case of HPSN and alumina-titanium nitride composites, abrasive wear and wear due to microfracture were the main wear mechanisms. Wear of the steel ball was lowest when in contact with HPSN---TiC composites, being almost equal to that of the ceramic, whereas the alumina-titanium nitride composite wore away the steel almost 20 times faster than the ceramic and will thus be unsuitable as a counterface material for 52100 steel.
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| 2. |
- Afroze, Shammya, 1987, et al.
(författare)
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Structure-conductivity relationship of PrBaMnMoO 6-δ through in-situ measurements: A neutron diffraction study
- 2021
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Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 47:1, s. 541-546
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Tidskriftsartikel (refereegranskat)abstract
- The structural and electrochemical properties of the double perovskite-type oxide, PrBaMnMoO6-δ, was investigated using neutron diffraction with in-situ conductivity measurement under a dry Argon atmosphere from 25 °C to 700 °C. A Rietveld refinement of the neutron diffraction data confirmed monoclinic symmetry in the P21/n space group. Rietveld refinement also confirms the unit cell parameters of a = 5.6567 (1) Å, b = 5.6065 (2) Å, c = 7.9344 (1) Å and β = 84.43° with reliable atomic positions and refinement factors (R-factors). Neutron diffraction data refinement shows two minor phases (<5%), an orthorhombic AB2O5 type phase of PrMn2O5 in the Pbam (No. 32) space group with unit cell parameters, a = 7.9672 (1) Å, b = 8.9043 (2) Å and c = 5.8540 (1) Å and a scheelite phase of BaMoO4 in the tetragonal I41/a (88) space group with the unit cell parameters, a = b = 5.9522 (1) Å, and c = 12.3211 (2) Å. Morphological images revealed a porous and intertwined microstructure. In-situ conductivity measurement shows that the total conductivity of this material was 130.84 Scm−1 at 700 °C.
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| 3. |
- Aleni, Afshin H., et al.
(författare)
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3D printing of dense and porous TiO2 structures
- 2020
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 46:10, s. 16725-16732
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Tidskriftsartikel (refereegranskat)abstract
- Direct foam writing allows the fabrication of highly porous and hierarchical ceramic structures with high specific mechanical properties. This manufacturing technique, however, has mainly used stabilized Al2O3 foam inks. In this work, we pressent a novel foam ink based on TiO2. This ink uses polyvinyl alcohol (PVA) as a binder and a small amount of zinc as a frothing agent. We used this ink to produce cylindrical foam samples via direct foam writing. The foams had a porosity of up to 65% and a mean pore size of 180 μm, which is significantly larger than previously reported for direct foam writing with Al2O3. The foams were tested in compression and were found to have an elastic modulus of 0.5 GPa and a compressive strength of 12–18 MPa. These mechanical properties are similar to those of porous ceramics produced by conventional manufacturing routes. Therefore, this work represents a step forward by broadening the direct foam writing process to a wider range of porous ceramics.
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| 4. |
- Ali, Amjad, et al.
(författare)
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A potential electrolyte (Ce1-x CaxO2-delta) for fuel cells:Theoretical andexperimental study
- 2018
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Ingår i: Ceramics International. - : ELSEVIER SCI LTD. - 0272-8842 .- 1873-3956. ; 44:11, s. 12676-12683
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Tidskriftsartikel (refereegranskat)abstract
- First-principles calculations are performed using density function theory to explore the effects of dopant Ca in ceria (Ce1-x CaxO2-delta). The impact of oxygen vacancy on band gap and density of states is examined in doped ceria using generalized gradient approximations. Vacancy association and vacancy formation energies of the doped ceria are calculated to reveal the effect of dopant on ion conduction. The experimental study of the sample Ce0.875Ca0.125O2-delta) was performed to compare with the theoretical results. The obtained results from theoretical calculation and experimental techniques show that oxygen vacancy increases the volume, lattice constant (5.47315 angstrom) but decrease the band gap (1.72 eV) and bulk modulus. The dopant radius (1.173 angstrom) and lattice constant (5.4718 angstrom) are also calculated by equations which is close to the DFT lattice parameter. The result shows that oxygen vacancy shifts the density of states to lower energy region. Band gap is decreased due to shifting of valence states to conduction band. Vacancy formation shows a significance increase in density of states near the Fermi level. Density of states at Fermi level is proportional to the conductivity, so an increase in density of states near the Fermi level increases the conductivity. The experimental measured ionic conductivity is found to 0.095 S cm(-1) at 600 degrees C. The microstructural studies is also reported in this work.
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| 5. |
- Ali, Sharafat, 1976-, et al.
(författare)
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Issues associated with the development of transparent oxynitride glasses
- 2015
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 41:3, s. 3345-3354
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Tidskriftsartikel (refereegranskat)abstract
- Oxynitride glasses and glass ceramics are increasingly recognized as potential materials in specialist applications in modern industrial sectors. Oxynitride glasses have superior mechanical, rheological and optical properties to their oxide glass counterparts. Properties of these glasses can be tailored by changes in nitrogen content and additions of various alkaline-earth and or rare-earth elements. In contrast to oxide glasses, oxynitride glasses are difficult to prepare which adds to production costs. Furthermore, they contain impurities in the form of elemental silicon and silicides, have poor oxidation resistance in air above their glass transition temperatures and have poor transparency in the visible region. This article reviews the above issues in relation to the potential applications of these glasses.
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| 6. |
- Alsalmah, Hessa A., et al.
(författare)
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Optical, conductivity, dielectric, and magnetic properties of polymer nanocomposite based on PAM/cs matrix and ZnFe2O4 NPs for use in magneto-electronic and energy storage capacitor devices
- 2024
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Ingår i: Ceramics International. - : ELSEVIER SCI LTD. - 0272-8842 .- 1873-3956. ; 50:7, s. 12167-12174
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a cast synthesis approach was used to create flexible nanocomposite films made of polyacrylamide (PAM), chitosan (Cs), and zinc ferrite nanoparticles (ZnFe2O4 NPs). XRD analysis was used to examine the composite structure. They demonstrated the effective interaction between ZnFe2O4 NPs and PAM/Cs blend. As the concentration of nanomaterial in the host polymer matrix grew, it was observed that the PAM/Cs matrix's direct and indirect energy band gaps decreased while its absorbance of ultraviolet-visible radiations increased. The nanocomposite's AC conductivity was significantly higher than that of the blend, and 2.5 wt percent of the nanocomposite showed the highest electrical conductivity. It was observed that as frequency raised, the epsilon ' and epsilon '' declined though the concentration of nanoparticles enhanced these characteristics. Because of the high dielectric permittivity of ZnFe2O4, the values of epsilon ' and epsilon '' raised as ZnFe2O4 were higher. The outcome of the vibrating sample magnetometer (VSM) demonstrated the ferromagnetic property of the produced nanocomposites. Furthermore, the VSM study shows that as the nanoparticles content increases, the PAM/Cs/ZnFe2O4 nanocomposites' Ms, Hc, and Mr also increase. These PAM/Cs/ZnFe2O4 films were shown by the experimental results to be promising candidates for bandgap-regulated materials, electromagnetic interference shielders, frequency tunable nanodielectric, and flexible dielectric substrates for future microelectronic, optoelectronic technologies, and capacitive energy storage.
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| 7. |
- Antti, Marta-Lena, et al.
(författare)
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Phase reactions in a hot pressed TiC/Si powder mixture
- 2012
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Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 38:3, s. 1999-2003
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Tidskriftsartikel (refereegranskat)abstract
- This work investigated the possibility of producing dense Ti3SiC2 by hot pressing TiC/Si powders. A hot press with graphite heating elements was used for densification and the phase reactions of some hot pressed samples were further evaluated by pressureless heating in a dilatometer. The density and phase composition of the heat treated samples were evaluated using Archimedes principle and by x-ray diffractometry respectively. Hot pressing resulted in a low Ti3SiC2 yield; the main phases were TiC and TiSi2 regardless of starting powder composition, temperature, holding time or pressure. A second heating without pressure resulted in Ti3SiC2 formation, but only in samples initially hot pressed at 1300 °C or lower. At higher hot pressing temperatures, thin oxide layers on particle surfaces were locked into the structure. Acting as diffusion barriers, they prevented the Ti3SiC2 forming reaction. In hot pressed samples the density was significantly higher than in samples sintered without pressure.
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| 8. |
- Archana, M. S., et al.
(författare)
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Influence of applied pressure during field-assisted sintering of Ti(C,N)-WC-FeAl based nanocomposite
- 2015
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Ingår i: Ceramics International. - 0272-8842 .- 1873-3956. ; 41:2, s. 1986-1993
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Tidskriftsartikel (refereegranskat)abstract
- Ti(C,N)-WC-FeAl based nanocomposites are processed by field-assisted sintering at 1500 degrees C. The phase and microstructural evolution during the process under the influence of different applied pressures of 30, 50 and 100 MPa are studied using x-ray diffraction and scanning electron microscopy. Lattice parameters of (Ti,W)(C,N) solid solution and binder phases after sintering are found to vary with applied pressure. The nanocomposite grains are observed to possess a core-rim microstructure. Microstructural variations in terms of type, size and fraction of "corerim" structure as a function of applied pressure are investigated. The hardness and indentation fracture toughness values are in the range of 17.6-18.4 GPa and 5.9-6.8 MPa root m, respectively. These values are comparable with those reported for Ti(C,N)-based composites with metal binder. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
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| 9. |
- Barick, P., et al.
(författare)
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Effect of concentration and molecular weight of polyethylenimine on zeta potential, isoelectric point of nanocrystalline silicon carbide in aqueous and ethanol medium
- 2015
-
Ingår i: Ceramics International. - : Elsevier Ltd. - 0272-8842 .- 1873-3956. ; 41:3, s. 4289-4293
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Tidskriftsartikel (refereegranskat)abstract
- The effect of dispersant concentration and its molecular weight on zeta potential of nanocrystalline silicon carbide in an aqueous medium was investigated. An increase in the concentration of the dispersant, such as polyethylenimine (PEI), in slurry prepared from nanosized silicon carbide, was found to augment the iso-electric point and zeta potential. However, the zeta potential was observed to decline as the pH of the slurry shifts towards the basic region. This aforementioned behavior is attributed to the enhanced mutual repulsion between the polymer chains of the dispersant adsorbed on the surfaces of SiC particles and those approaching the surfaces. The higher ionization potential of polymers in the acidic region compared to the basic region increases the adsorption. The relationship between zeta potential and pH is however, noted to remain virtually unchanged with molecular weight of PEI. Further, it is observed that zeta potential of SiC decreases with the increase in solid content of the slurry. Rheology study reveals that the ethanol based slurry has a lower viscosity than the water based slurry, making ethanol the preferred dispersing medium for colloidal processing of nanometric SiC powder. © 2014 Elsevier Ltd and Techna Group S.r.l.
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| 10. |
- Barick, Prasenjit, et al.
(författare)
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Effect of pressure and temperature on densification, microstructure and mechanical properties of spark plasma sintered silicon carbide processed with β-silicon carbide nanopowder and sintering additives
- 2016
-
Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 42:3, s. 3836-3848
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Tidskriftsartikel (refereegranskat)abstract
- The effects of applied pressure and temperature during spark plasma sintering (SPS) of additive-containing nanocrystalline silicon carbide on its densification, microstructure, and mechanical properties have been investigated. Both relative density and grain size are found to increase with temperature. Furthermore, with increase in pressure at constant temperature, the relative density improves significantly, whereas the grain size decreases. Reasonably high relative density (~96%) is achieved on carrying out SPS at 1300 °C under applied pressure of 75 MPa for 5 min, with a maximum of ~97.7% at 1500 °C under 50 MPa for 5 min. TEM studies have shown the presence of an amorphous phase at grain boundaries and triple points, which confirms the formation of liquid phase during sintering and its significant contribution to densification of SiC at relatively lower temperatures (≤1400 °C). The relative density decreases on raising the SPS temperature beyond 1500 °C, probably due to pores caused by vaporization of the liquid phase. Whereas β-SiC is observed in the microstructures for SPS carried out at temperatures ≤1500 °C, α-SiC evolves and its volume fraction increases with further increase in SPS temperatures. Both hardness and Young׳s modulus increase with increase in relative density, whereas indentation fracture toughness appears to be higher in case of two-phase microstructure containing α and β-SiC.
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| 11. |
- Batool, S S., et al.
(författare)
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Investigation of dielectric relaxation behavior of electrospun titanium dioxide nanofibers using temperature dependent impedance spectroscopy
- 2013
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 39:2, s. 1775-1783
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Tidskriftsartikel (refereegranskat)abstract
- The electrospinning method has been utilized in the fabrication of titanium dioxide nanofibers (TNFs) with an average diameter of similar to 50 nm and length of 100 um. Effect of temperature on the dielectric relaxation behavior of the fabricated nanofibers have been studied using AC impedance spectroscopy. The morphological, structural and compositional aspects as well as the optical properties of the TNFs have been investigated by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy-dispersive x-ray spectroscopy (EDX) and ultraviolet visible (UV vis) absorption spectrum. The permittivity behavior of the device at the frequency below 10(2) Hz shows the relaxation contribution along with the electrode polarization. Dielectric loss peak in loss tangent also confirms the presence of relaxing dipoles in TNFs. The AC conductance as a function of frequency confirms the semiconducting nature of TNFs and obeys Jonschers power law except a small deviation in the low frequency region. DC conductivity increases with increase in temperature.
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| 12. |
- Berg, Camilla, et al.
(författare)
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Bulk nanobubbles as soft templates in the fabrication of inorganic core-shell particles
- 2023
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 49:11, s. 16501-16513
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Forskningsöversikt (refereegranskat)abstract
- Hollow microstructured-and nanostructured-materials (also known as core-shell particles) have got great attention as advanced materials due to their fascinating physicochemical properties and favourable application prospects in many fields. In recent years, a variety of synthesis strategies have been explored to fabricate core-shell particles with different morphologies, compositions, microstructures, and thereby versatile functionalities. Among the synthesis strategies, soft-templating with the usage of nanobubbles is a feasible and effective one. Many inorganic core-shell particles have been prepared by using nanobubbles as a template. Nevertheless, studies in this field have not been reviewed comprehensively yet. Herein, the paper firstly reviewed several critical aspects of nanobubbles, such as the formation methods, stability and stabilization strategies of nano-bubbles; Secondly, characteristics of core-shell particles prepared by using nanobubbles soft template were summarized, including formation mechanisms, morphologies, etc.; Lastly, concerns regarding nanobubbles as soft templates were also briefly discussed.
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| 13. |
- Berg, Camilla, et al.
(författare)
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Electron microscopy evaluation of mineralization on peritubular dentin with amorphous calcium magnesium phosphate microspheres
- 2020
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Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 46:11, s. 19469-19475
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Tidskriftsartikel (refereegranskat)abstract
- Dentin hypersensitivity can be reduced by the use of a remineralization agent to hinder movement of fluids within the dentin tubules. Penetration of particles into the tubules and a continuous release of Ca2+ and phosphate ions can induce the mineralization of a material mimicking the mineral component of dentin, sealing the tubules. In this work, we have used complementary electron microscopy techniques to investigate the ultrastructure of dentin and crystallization and occlusion effects when using amorphous calcium magnesium phosphate (ACMP) microspheres on extracted human molars. Application of the particles in a gel intended for athome use resulted in intra-tubular mineralization of a carbonate substituted hydroxyapatite (HA). Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that crystallization was initiated on the peritubular dentin (PTD) with undirected crystal growth leading to the formation of a porous material. We additionally investigated the effects from using a fluoride toothpaste to potentially improve the remineralization and anti-cariogenic properties of the ACMP microspheres. Energy dispersive x-ray spectroscopy (EDX) using TEM in scanning mode (STEM) showed that fluoride incorporation resulted in an increase in aspect ratio of the crystals, crystal growth directed towards the center of the tubule lumen and densification of the mineralized material. Thus, ACMP microspheres are promising alternatives as occluding agents and the efficacy of the particles could be further improved with the complementary use of a fluoride toothpaste.
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| 14. |
- Berg, Camilla, et al.
(författare)
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Ion substitution induced formation of spherical ceramic particles
- 2019
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Ingår i: Ceramics International. - : ELSEVIER SCI LTD. - 0272-8842 .- 1873-3956. ; 45:8, s. 10385-10393
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Tidskriftsartikel (refereegranskat)abstract
- How to precipitate ceramic nano- and microspheres in water based solutions only using inorganic ions is a challenge. In this study, spherical particles of alkaline earth phosphates and fluorides were synthesized using a precipitation reaction. Substituting ions, through inhibition of crystal growth, was used to induce sphere formation and to alter the morphology, size and composition of the spheres. The difference in ionic radius between the substituting ion (Mg, Ca and Sr) and the main cation (Sr and Ba) influenced the critical concentration to allow for sphere formation as well as the crystallinity. The larger difference, the lower was the concentration needed to form spheres. Low concentrations of Mg was enough to generate amorphous spheres of Sr- and Ba- phosphates whereas higher concentrations were needed if the radius difference were smaller. An increasing degree of substitution leads to a decrease in crystallinity of precipitated particles. The degree of substitution was determined to 16-55% where a low degree of ion substitution in the phosphates resulted in the formation of spheres (500-800 nm) with rough surfaces composed of apatite like phases. A higher degree of substitution resulted in amorphous spheres (500 nm- (1) mu m) with smooth surfaces.
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| 15. |
- Bhatti, Muhammad Ali, et al.
(författare)
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Efficient photo catalysts based on silver doped ZnO nanorods for the photo degradation of methyl orange
- 2019
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Ingår i: Ceramics International. - Oxford : Elsevier. - 0272-8842 .- 1873-3956. ; 45:17, Part B, s. 23289-23297
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the doped ZnO nanorods with silver (Ag) as photosensitive material are prepared by the solvothermal method. The structural and optical characterization is carried out by the scanning electron microscopy, X-ray diffraction, energy dispersive spectroscopy and UV–visible spectroscopy. The use of Ag as dopant did not alter the morphology of ZnO except sample 4 which has flower like morphology. The Ag, Zn and O are the main constituent of doped materials. The XRD revealed a hexagonal phase for ZnO and cubic phase for silver and confirmed the successful doping of Ag. The photocatalytic activity of Ag doped ZnO nanorods was investigated for the photo degradation of methyl orange. The photocatalytic measurements show that 88% degradation of methyl orange by the sample 4 within the 2 h of UV light treatment (365 nm) is significant advancement in the photocatalyst and provide the inexpensive and promising materials for the photochemical applications. © 2019 Elsevier Ltd and Techna Group S.r.l.
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| 16. |
- Bu, Junfu, et al.
(författare)
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Preparation of 30 mol.% Y-doped hafnia (Hf0.7Y0.3O2-delta) using a modified solid-state reaction method
- 2015
-
Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 41:2, s. 2611-2615
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Tidskriftsartikel (refereegranskat)abstract
- A pure and well-crystallized Hf0.7Y0.3O2-delta (YSH) powder was synthesized using a modified solid-state reaction method. Water-based milling and freeze drying process were implemented to facilitate powder synthesis and final densification process. The improved powder performance, in aspects of phase development and sintering behaviour, was investigated by systematic comparison between different powder processing procedures. Dense YSH ceramic material with a relative density of 0.975 was successfully obtained using conventional sintering at 1650 degrees C for 10 h. XRD, SEM and EDS were employed to characterize the synthesized powder and dense YSH ceramics. Dense YSH ceramic possesses a fluorite cubic structure with an a value of 5.1406 angstrom, and the ionic radius of Y3+ in YSH was determined to be 0.1006 nm.
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| 17. |
- Bu, Junfu, et al.
(författare)
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Sintering behaviour of the protonic conductors BaZr(x)Ce(0.8-x)Ln(0.2)O(3-delta) (x=0.8, 0.5, 0.1; Ln=Y, Sm, Gd, Dy) during the solid-state reactive-sintering process
- 2015
-
Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 41:2, s. 2558-2564
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Tidskriftsartikel (refereegranskat)abstract
- The protonic conductors BaZr(x)Ce(0.8-x)Ln(0.2)O(3-delta) (x=0.8, 0.5, 0.1; Ln=Y, Sm, Gd, Dy) were successfully prepared using a solid-state reactive-sintering method. NiO (1 wt.%) was added as a sintering aid, and it was proven that NiO produced tremendous enhancement in the densification process. The morphologies of the variously doped BaZr(0.8)Ln(0.2)O(3-delta), BaZr(0.5)Ce(0.3)Ln(0.2)O(3-delta) and BaZr(0.1)Ce(0.7)Ln(0.2)O(3-delta) ceramics, as well as their sintering behaviour, were investigated. The results show that the Ce content in the BaZr(0.8)Ln(0.2)O(3-delta), BaZr(0.5)Ce(0.3)Ln(0.2)O(3-delta) and BaZr(0.1)Ce(0.7)Ln(0.2)O(3-delta) compounds influences the sintering temperature significantly, and a larger Ce content will lead to a lower sintering temperature. In addition, ionic radii of the dopants that are similar to the ionic radii of the B-site will also result in a lowered sintering temperature. Based on the present study, NiO has no influence on the lattice parameters.
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| 18. |
- Bu, Junfu, et al.
(författare)
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Transport properties of BaZr0.5Ce0.3Y0.2O3-δ proton conductor prepared by spark plasma sintering
- 2016
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 42:3, s. 4393-4399
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Tidskriftsartikel (refereegranskat)abstract
- Dense BaZr0.5Ce0.3Y0.2O3-δ (BZCY532) proton conductors were prepared by a spark plasma sintering method. Their conductivities were determined in different atmospheres: dry air, wet N2 and wet H2. Moreover, the potential electronic conductivity contribution to the total conductivity was also identified by testing their total conductivities at different oxygen partial pressures (1-10-24 atm) in combination with an XPS analysis. It is found that the prepared dense BZCY532 ceramics are good proton conductors at 600 °C. In addition, the Ce3+ concentration in the dense BZCY532 ceramics is around 3.5 atm% of the total Ce element, and the electronic contribution to the total conductivity can be neglected after a postheat treatment.
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| 19. |
- Chen, Qingguo, et al.
(författare)
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Preparation and properties of Ce0.5Nd0.5PO4 monazite ceramics by pressureless sintering and spark plasma sintering (SPS)
- 2024
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 50:12, s. 20803-20810
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Tidskriftsartikel (refereegranskat)abstract
- LnPO4·nH2O rhabdophane/monazite is an important actinide-bearing material in the back end of the nuclear fuel cycle. In this work, using Nd3+ to simulate trivalent actinides, Ce0.5Nd0.5PO4·0.667H2O rhabdophane was synthesized by the wet-chemistry method in 90 °C and pH = 1 solution. The sintering behavior of associated Ce0.5Nd0.5PO4 monazite ceramics was investigated by pressureless sintering and spark plasma sintering (SPS), along with appraising their chemical stability. The results reveal that Ce3+ is successfully replaced by Nd3+ in the rhabdophane lattice, and rhabdophane can transform to monazite with a temperature over 750 °C. SPS can compact the ceramic sample at a lower temperature compared to pressureless sintering even if the grain size is smaller. Adding a pre-sintering process of 900 °C before SPS and pressureless sintering will further improve the density and Vickers hardness of ceramics. For the chemical stability of Ce0.5Nd0.5PO4 monazite ceramics, Ce is more likely to be leached compared to Nd, and the ceramics prepared by SPS with a pre-sintering process have the lowest normalized leaching rates, associated with the values of 2.03 × 10−5 g·m−2·d−1 and 0.75 × 10−5 g·m−2·d−1 for Ce and Nd, respectively.
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| 20. |
- Chen, Song, et al.
(författare)
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Eu3+ doped monetite and its use as fluorescent agent for dental restorations
- 2018
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Ingår i: Ceramics International. - : Saunders Elsevier. - 0272-8842 .- 1873-3956. ; 44:9, s. 10510-10516
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Tidskriftsartikel (refereegranskat)abstract
- It is essential but challenging to distinguish the dental restorations from the surrounding teeth when removing filling materials from cavity. In this study, Eu3+ doped monetite was proposed as a fluorescent agent for dental restorations to meet this challenge. Eu3+ doped monetite with enhanced fluorescent property was obtained via a precipitation method. The presence of Eu3+ could prevent the phase transformation of brushite to monetite. However, all the brushite particles transformed to monetite at 300 °C and to tricalcium phosphate at 800 °C. The emission intensity increased with the addition of Eu3+ and reached the maximum when 12 mol% Eu3+ was added into the aqueous solution. With either 254 nm or 393 nm excitation, Eu3+ doped monetite showed the strongest fluorescence emission peaking at 616 nm and other two moderate bands peaking at 699 nm and 593 nm. The excitation spectra at the emission wavelength of 616 nm showed strong absorption peaks at 254 nm and 393 nm. We further investigate the fluorescence properties of Eu3+ doped monetite in one type of dental restorations. Glass ionomer cement with Eu3+ doped monetite exhibited clear fluoresce with origin color under UV irradiation at 254 nm, showing that Eu3+doped monetite is a promising fluorescent agent for dental restorations.
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| 21. |
- Cheng, Z., et al.
(författare)
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Ink-jet printed BNT thin films with improved ferroelectric properties via annealing in wet air
- 2018
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 44:9, s. 10700-10707
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Tidskriftsartikel (refereegranskat)abstract
- In this work, an ink-jet printing process based on the sol-gel route was applied to prepare lead-free ferroelectric Na0.5Bi0.5TiO3(BNT) thin films for the first time. Dense and crack-free films with perovskite structure were obtained from a modified precursor solution through multiple printing and pyrolysis processes. The ferroelectric, dielectric and electrical properties were significantly affected by the annealing temperature and atmosphere. The film annealed at 670 °C in wet air showed a high remnant polarization of 24.7 μC/cm2 with a low coercive field of 263 kV/cm, the dielectric constant and loss were 185 and 0.1 at 10 kHz, respectively. It was found that wet air was an alternative to reduce oxygen vacancies and enhance properties of ferroelectric films, which can be explained by the defect chemical reaction between water and oxygen vacancies. X-ray photoelectron spectroscopy(XPS) confirmed the decrease of oxygen vacancies after annealing with water presence, with a formation of Ohmic conduction mechanism dominated by charged hydroxyl groups.
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| 22. |
- Choopani, S., et al.
(författare)
-
Ferromagnetic resonance and magnetic anisotropy in biocompatible Y3Fe5O12@Na0.5K0.5NbO3 core-shell nanofibers
- 2019
-
Ingår i: Ceramics International. - : Elsevier Ltd. - 0272-8842 .- 1873-3956. ; 46:2, s. 2072-2078
-
Tidskriftsartikel (refereegranskat)abstract
- Y3Fe5O12@Na0.5K0.5NbO3 (YIG@NKN) core-shell nanofibers were synthesized by the coaxial electrospinning technique. For comparison, samples of YIG and NKN nanofibers were prepared. Scanning Electron Microscopy (SEM) and 3D laser-scanning confocal microscopy (TDLM) of YIG@NKN nanofibers revealed long uniform size distributed fibers with the average diameter of 100–150 nm. X-Ray diffraction (XRD) examination shows the existence of the distinct peaks of orthorhombic NKN and cubic YIG. Magnetic force microscopy (MFM) of individual YIG@NKN nanofiber demonstrates a magnetic core that is extended in one half of the diameter of the fiber. These nanofibers show obvious Ferromagnetic resonance (FMR) with resonance near 2 KOe similar to YIG fibers but in such a way that it starts to increase linearly with applying magnetic field from zero up to near resonance field. Also they show a soft magnetic behavior with saturation magnetization of 10 emu/gr. Furthermore, we propose a model to explain line shape of randomly oriented fibers and extract all the magnetic anisotropy parameters from FMR data. The results rely the shape anisotropy as dominant effect, however the dipolar field among fibers should be considered. The highest degree of asymmetry observed in the case of core-shell fibers in hard direction that it can be originated from magneto electric effects. By taking into account the observed FMR, the ability of adequate control of microwave absorption by applying magnetic field and biocompatibility, the synthesized core-shell nanofibers are the most promising candidate for clinical application such as microwave cancer thermotherapy and adjustable microwave absorbers.
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| 23. |
- Dahl, P., et al.
(författare)
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Densification and properties of zirconia prepared by three different sintering techniques
- 2007
-
Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 33:8, s. 1603-1610
-
Tidskriftsartikel (refereegranskat)abstract
- Densification of nanocrystalline yttria stabilized zirconia (YSZ) powder with 8 mol% Y2O3, prepared by a glycine/nitrate smoldering combustion method, was investigated by spark plasma sintering, hot pressing and conventional sintering. The spark plasma sintering technique was shown to be superior to the other methods giving dense materials (>= 96%) with uniform morphology at lower temperatures and shorter sintering time. The grain size of the materials was 0.21, 0.37 and 12 mu m after spark plasma sintering, hot pressing and conventional sintering, respectively. Total electrical conductivity of the materials showed no clear correlation with the grain size, but the activation energy for spark plasma sintered materials was slightly higher than for materials prepared by the two other densification methods. The hardness, measured by the Vickers indentation method, was found to be independent on grain size while fracture toughness, derived by the indentation method, was slightly decreasing with increasing grain size.
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| 24. |
- Dey, J., et al.
(författare)
-
Non-collinear magnetic structure of the MAX phase Mn2GaC epitaxial films inferred from zero-field NMR study (CE-5:L05)
- 2023
-
Ingår i: Ceramics International. - : ELSEVIER SCI LTD. - 0272-8842 .- 1873-3956. ; 49:14, s. 24235-24238
-
Tidskriftsartikel (refereegranskat)abstract
- Zero-field NMR investigations on the 69Ga, 71Ga, and 55Mn nuclei have been performed at 4.2 K on a 100 nm thick epitaxial Mn2GaC(0001) MAX phase film grown on a MgO(111) substrate. This nano-laminated structure consists of ferromagnetic Mn-C-Mn stacks interleaved with monolayers of gallium. A resolved quadrupolar structure of the observed gallium resonances is a fingerprint of a well-defined crystal field confirming high crystal quality. The nuclei of non-magnetic gallium atoms are shown to experience the transferred hyperfine magnetic field of 15.75 T (& PLUSMN;0.05 T), which is due to polarization of their 4s electron shell by the magnetic moments of manganese neighbors, evidencing the presence of an uncompensated ferromagnetic moment within the manganese sublattice. The average magnetic moment of manganese was found to be around 2 & mu;B, strongly contrasting with the reported remnant magnetization of only 0.3 & mu;B. Moreover, the 55Mn NMR spectrum in-dicates the presence of magnetically non-equivalent manganese sites within this structure. The observed features of the 69,71Ga and 55Mn NMR spectra cannot be reconciled with any of the hitherto proposed collinear ar-rangements of manganese moments and suggest their non-collinear arrangement across a gallium layer. Nevertheless a more advanced study is required to elucidate the detailed nature of magnetic structure in this material.
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| 25. |
- Dziewanowska, Julia, et al.
(författare)
-
Nanocrystallization as a tool for controlling in vitro dissolution of borophosphate glass
- 2023
-
Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 49:16, s. 27382-27390
-
Tidskriftsartikel (refereegranskat)abstract
- The controlled nanocrystallization of sodium-calcium-borophosphate glass (Na16.6Ca5.1B10.5Al0.8P10.5 O56.5 in at %) was conducted to investigate its influence on in vitro dissolution. Three temperatures (570 degrees C, 590 degrees C, and 610 degrees C) were selected based on thermal analysis and investigation of the morphology, structure, and in vitro dissolution of glass and glass-ceramics was conducted. The results of X-ray diffraction confirmed the presence of calcium phosphates nanocrystallites in glass-ceramics, with their contents increasing proportionally to the crystallization temperature. Infrared spectroscopy showed the presence of phosphate and borate network units, along with phosphates in a crystalline form. It was found that the target glass shows the highest mass loss in comparison to the glass-ceramics. Controlled nanocrystallization slowed down the dissolution of the materials (>10%), but did not adversely affect the deposition of hydroxyapatite layer. The presence of calcium phosphate nanocrystallites favors the process of B3+ release. The nanocrystallization of borophosphate glasses is a perspective tool for controlling the rate of dissolution of bioactive materials and enhancing their ability to de-posit hydroxyapatite on their surface.
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| 26. |
- Ebin, Burcak, et al.
(författare)
-
Preparation and electrochemical properties of spinel LiFexCuyMn1.2O4 by ultrasonic spray pyrolysis
- 2014
-
Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 40:1, s. 1019-1027
-
Tidskriftsartikel (refereegranskat)abstract
- Nanocrystalline LiFexCuyMn1.2O4 (x and y=0.2, 0.4 and 0.6) particles were prepared by the ultrasonic spray pyrolysis method using nitrate salts at 800 degrees C in air atmosphere. Particle properties were characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. Also, cyclic voltammetry and galvanostatic tests were performed to investigate the effects of the double substituent and doping amounts on electrochemical behavior. Results show that the aggregation of nanocrystallites around 90 nm size formed submicron spherical cathode particles. Transition metal ratios in particles exhibited a perfect fit with desired amounts. Although the change of iron and copper amounts do not show significant differences in the particle size and shape morphology, they modify the 4 V and 3 V potential plateaus of spinel LiMn2O4. The discharge capacities of LiFe0.2Cu0.6Mn1.2O4 particles are 39 and 23 mAh g(-1) for 4 and 2.6 V potential regions, respectively. 4 V discharge capacity disappeared with increasing of iron and decreasing of copper contents due to random occupation of iron and copper ions in the spinel lattice.
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| 27. |
- Elbadawi, Mohammed, 1987-, et al.
(författare)
-
Guar Gum: A Novel Binder for Ceramic Extrusion
- 2017
-
Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 43:18, s. 16727-16735
-
Tidskriftsartikel (refereegranskat)abstract
- Ceramic honeycomb extrusion is a technique capable of attaining high strength, porous ceramics. However, challenges prevent the realisation of its potential. These include the design of an intricate honeycomb die and the formulation of an extrudable paste. The present study addresses the latter by using guar gum (GG) as a binder. GG was rationally selected because hydrogels thereof exhibit strong shear-thinning and high stiffness properties, which are required for extrusion. Rheological analyses demonstrated ceramic pastes with similar qualities were achieved, with hydroxyapatite (HA) used as the model ceramic. The shear stiffness modulus of HA pastes was determined as 8.4 MPa with a yield stress of 1.1 kPa. Moreover, this was achieved with GG as the sole additive, which further facilitates the overall fabrication process. The binder extraction notably occurred at relatively low temperatures when other high molecular weight polymers demand temperatures above 1000 °C; therefore the latter precludes the use of ceramics with low sintering onset. The process culminated in a porous HA scaffold with similar porosity to that of a commercial HA graft, but with higher compressive strength. Lastly, the study notes that the biological and water-soluble properties of GG can broaden its application into other ceramic fabrication processes.
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| 28. |
- Enrichi, Francesco, et al.
(författare)
-
Ag-sensitized Tb3+/Yb3+ codoped silica-zirconia glasses and glass-ceramics : systematic and detailed investigation of the broadband energy-transfer and downconversion processes
- 2021
-
Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 47:13, s. 17939-17949
-
Tidskriftsartikel (refereegranskat)abstract
- Various studies report that Tb3+/Yb3+ co-doped materials can split one UV or 488 nm (visible) photon in two near infrared (NIR) photons at 980 nm by an energy-transfer process involving one Tb3+ and two Yb3+ ions. Additionally, it was demonstrated that Ag multimers can provide an efficient optical sensitizing effect for rare earth ions (RE3+ ions), resulting in a broadband enhanced excitation, which could have a significant technological impact, overcoming their limited spectral absorptions and small excitation cross sections. However, a systematic and detailed investigation of the down-conversion process enhanced by Ag nanoaggregates is still lacking, which is the focus of this paper. Specifically, a step by step analysis of the energy-transfer quantum-cutting chain in Ag-exchanged Tb3+/Yb3+ co-doped glasses and glass-ceramics is presented. Moreover, the direct Ag-Yb3+ energy-transfer is also considered. Results of structural, compositional, and optical characterizations are given, providing quantitative data for the efficient broadband Ag-sensitization of Tb3+/Yb3+ quantum cutting. A deeper understanding of the physical processes beneath the optical properties of the developed materials will allow a wiser realization of more efficient energy-related devices, such as spectral converters for silicon solar cells and light-emitting devices (LEDs) in the visible and NIR spectral regions.
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| 29. |
- Enrichi, Francesco, et al.
(författare)
-
Effect of the crystal structure on the optical properties and Ag sensitization of Tb3+/Yb3+ ions in silica-zirconia glasses and glass-ceramics
- 2022
-
Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 49:24 Part B
-
Tidskriftsartikel (refereegranskat)abstract
- The role of the material structure in the energy transfer between Ag and Tb3+/Yb3+ ions is studied in silica-soda-zirconia sol-gel glasses and glass-ceramics. The preparation of Tb3+ and Yb3+ doped silica-soda-zirconia layers was carried out by sol-gel and dip-coating, followed by thermal annealing. The precipitation of zirconia nanocrystals was obtained by controlling the annealing temperature: from a full amorphous glass at 700 °C into a glass-ceramic at 1000 °C. A different crystalline structure of zirconia nanocrystals, tetragonal or cubic, was controlled by the rare-earth doping and investigated in relation to the Tb3+/Yb3+ optical properties. Moreover, Ag codoping was introduced by ion-exchange, obtaining a significant photoluminescence enhancement, both in the intensity and in the broadness of the excitation band, covering the whole UV region and part of the violet-blue region. Ag-sensitized Tb3+/Yb3+ doped silica-soda-zirconia glass-ceramics were attested to be potential candidates for energy-related applications, such as spectral conversion layers for solar cells, lasers and light-emitting devices (LEDs) in the visible and NIR spectral regions.
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| 30. |
- Fu, Le, et al.
(författare)
-
New insights into the formation mechanism of zircon in a ZrO2-SiO2 nanocrystalline glass-ceramic : A TEM study
- 2022
-
Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 48:18, s. 27097-27105
-
Tidskriftsartikel (refereegranskat)abstract
- We have previously observed that doping of Ca ions was beneficial to the formation of zircon (ZrSiO4). It is well known that synthetic ZrSiO4 is typically formed via a solid-state reaction between ZrO2 and SiO2, in which the interfaces between the reactant and resultant play an important role. However, the interfaces are lacking detailed microstructural observation. This follow-up study aims at exploring the formation mechanism of ZrSiO4 by inspecting the interfaces at the nano and atomic scales with TEM techniques. Results demonstrated that ZrSiO4 was formed in the Ca-doped sample after sintering at 1200 ?, whereas, no ZrSiO4 was formed in the undoped sample even after sintering at 1230 ?. The Ca-doped sample consisted of a continuous ZrSiO4 matrix with dispersed ZrO2 nanocrystallites. Doping of Ca ions promoted the formation of ZrSiO4 by causing lattice distortion and oxygen vacancies in ZrO2 lattices. Thin amorphous grain boundary complexions were found between ZrO2 nanocrystallites and between ZrO2 and ZrSiO4 crystallites. These amorphous complexions acted as reaction sites and an intermediate metastable state for the solid-state reaction. A detailed formation mechanism of ZrSiO4 at the nanometer scale and atomic scale has been proposed.
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| 31. |
- Ganvir, Ashish, 1991-, et al.
(författare)
-
Effect of suspension characteristics on the performance of thermal barrier coatings deposited by suspension plasma spray
- 2020
-
Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 47:1, s. 272-283
-
Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the influence of suspension characteristics on microstructure and performance of suspensions plasma sprayed (SPS) thermal barrier coatings (TBCs). Five suspensions were produced using various suspension characteristics, namely, type of solvent and solid load content, and the resultant suspensions were utilized to deposit five different TBCs under identical processing conditions. The produced TBCs were evaluated for their performance i.e. thermal conductivity, thermal cyclic fatigue (TCF) and thermal shock (TS) lifetime. This experimental study revealed that the differences in the microstructure of SPS TBCs produced using varied suspensions resulted in a wide-ranging overall TBC performance. All TBCs exhibited thermal conductivity lower than 1 W/(m. K) except water-ethanol mixed suspension produced TBC. The TS lifetime was also affected to a large extent where 10 wt % solid loaded ethanol and 25 wt % solid loaded water suspensions produced TBCs exhibited the highest and the lowest lifetime, respectively. On the contrary, TCF lifetime was not as significantly affected as thermal conductivity and TS lifetime, and all ethanol suspensions showed marginally better TCF lifetime than water and ethanol-water mixed suspensions deposited TBCs. © 2020
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| 32. |
- Ganvir, Ashish, 1991-, et al.
(författare)
-
Failure analysis of thermally cycled columnar thermal barrier coatings produced by high-velocity-air fuel and axial-suspension-plasma spraying : A design perspective
- 2018
-
Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 44:3, s. 3161-3172
-
Tidskriftsartikel (refereegranskat)abstract
- Axial-suspension-plasma spraying (ASPS) is a fairly recent thermal spray technology which enables production of ceramic top coats in TBCs, incorporating simultaneously the properties of both the conventional-plasma sprayed (highly insulating porous structures) and electron-beam-physical-vapor-deposited (strain-tolerant columnar structures) top coats. TBCs are required to insulate the hot components in a gas turbine engine against high temperature and harsh operating conditions. Periodic heating and cooling of turbine engines during operation can create severe thermal cyclic fatigue conditions which can degrade the performance of these coatings eventually leading to the failure. An in-depth experimental investigation was performed to understand the failure behavior of columnar TBCs subjected to thermal cyclic fatigue (TCF) test at 1100 C. The study revealed that the TCF performance was influenced to an extent, by the top coat microstructure, but was primarily affected by the severity of thermally grown oxide (TGO) growth at the bond coat-top coat interface. Mixed failure modes comprising crack propagation through the bond coat-TGO interface, through TGO and within the top coat were identified. Based on the analysis of the experimental results and thorough discussion a novel design of microstructure for the high TCF performance columnar TBC is proposed. © 2017 Elsevier Ltd and Techna Group S.r.l.
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| 33. |
- Gholizadeh, Armin, et al.
(författare)
-
Facile synthesis of nanographene by a high-yield and scalable method
- 2020
-
Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 46:14, s. 22861-22868
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this work was to synthesize nanographene (NG) through a simple, efficient, and cost-effective method. In this regard, a combination of microwave (MW) and shear mixing with a kitchen blender was used. Atomic force microscopy (AFM), Raman spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis were used to investigate the structure of synthesized NG. The Results of the characterizations demonstrated that most of the synthesized NG exhibited OD structure and bilayer characteristics. The obtained results introduce a method for synthesizing NG at a large scale through a combination of MW and shear, in a relatively short time, without any need for purification.
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| 34. |
- Govindan, V., et al.
(författare)
-
One-pot microwave synthesis of SnSe and Lanthanum doped SnSe nanostructure with direct Z scheme pattern for excellent photodegradation of organic pollutants
- 2022
-
Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 48:9, s. 12228-12239
-
Tidskriftsartikel (refereegranskat)abstract
- A novel nanostructure photocatalytic material was fabricated using Lanthanum doped SnSe by one-pot microwave method is reported to newest. Photocatalytic performance efficiency of pristine SnSe and Lanthanum doped SnSe nanostructures were investigated to degrade organic pollutants from wastewater. The crystal structure, morphology, and optical properties of the nanostructure were investigated using powder X-ray diffraction, field emission scanning electron microscope, UV–Vis, and PL spectral studies. Nano rods/spheres for pure SnSe were altered significantly leading to higher amounts of nanorods due to La doped and increase in concertation leads higher formation of nanorods. Increased in structure and morphology played a vital role in photocatalytic activity. Nanostructure exhibits enhanced physicochemical properties and showed an excellent synergetic effect demonstrating the effect of La (1, 3, and 5%) concentrations in SnSe nanostructure. The optical energy gap has a reducing trend due to the increment of doping concentration. The individual elements oxidation states were justified from X-ray photoelectron spectroscopical studies. Thermal stability and phase changes of the nanostructure before and after doping of La were evaluated through TGA/DTA analysis. From the photocatalytic measurement rare-earth (La) doped samples expressed higher catalytic nature than the pure SnSe. It was observed that the higher atomic element La had a significant role to produce a large number of electron-hole pair recombination and defective structure in the host lattice.
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| 35. |
- Guo, Hua, et al.
(författare)
-
Quantitative phase analyses of biomedical pyrophosphate-bearing monetite and brushite cements by solid-state NMR and powder XRD
- 2020
-
Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 46:8, s. 11000-11012
-
Tidskriftsartikel (refereegranskat)abstract
- We present a comprehensive composition analysis of calcium phosphate cements (CPCs) incorporating increasing amounts of bioactive pyrophosphate species (up to 17 wt% P2O7). These cements comprise primarily poorly ordered monetite (CaHPO4) or brushite (CaHPO4 center dot 2H(2)O) and are investigated for enhanced osteoinductive bone/tooth implants. The specimens were characterized by magic-angle spinning (MAS) P-31 and H-1 nuclear magnetic resonance (NMR) spectroscopy along with powder X-ray diffraction (PXRD). P-31 MAS NMR was employed to quantify the major monetite/brushite constituents, the crystalline and amorphous pyrophosphates, as well as various minor orthophosphate by-products. The NMR-derived contents of the crystalline phases accorded well with those from Rietveld analyses of the corresponding PXRD data. The amounts of crystalline and amorphous pyrophosphate depended on the precise cement precursor mixture and preparation conditions, which together with their distinct structural roles may enable the design of cements with a tunable P2O74 - release into aqueous solutions.
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| 36. |
- Gustafsson, Stefan, 1976, et al.
(författare)
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Alumina/silicon carbide composites fabricated via in situ synthesis of nano-sized SiC particles
- 2009
-
Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 35:3, s. 1293-1296
-
Tidskriftsartikel (refereegranskat)abstract
- Alumina/silicon carbide composites have been fabricated by a new technique involving the in situ synthesis of nano-sized SiC particles. A mixture of alumina powder and silicon carbide precursors was prepared in an aqueous suspension. Green bodies were formed by cold isostatic pressing of granules obtained by freeze granulation, and pressureless sintered at 1750 °C for 4 h in an argon atmosphere. Mullite (10-20 vol%) formed in addition to SiC during sintering. The SiC particles were located predominantly to the interior of the mullite and alumina matrix grains. © 2008 Elsevier Ltd and Techna Group S.r.l.
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| 37. |
- Horng, Ray-Hua, et al.
(författare)
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Ion implantation effects on the characteristics of 8-Ga2O3 epilayers grown on sapphire by MOCVD
- 2022
-
Ingår i: Ceramics International. - : ELSEVIER SCI LTD. - 0272-8842 .- 1873-3956. ; 48:24, s. 36425-36432
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, the Si-ions implantation technique with different doses from 1 x 1014 to 1 x 1015 cm-2 and dose energy 30, 40 and 50 keV was used to tune the electrical properties in unintentionally doped (UID) 8-Ga2O3 epilayers grown on the sapphire substrates by metalorganic chemical vapor deposition (MOCVD). A high quality UID 8-Ga2O3 epilayers were fabricated using the optimized growth parameters of MOCVD. The UID and Si-ions implanted 8-Ga2O3 epilayers were examined and results were compared with the help of X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. Si-ions implantation parameters were also simulated by stopping and range of ions in matter software (SRIM) and actual Si-ions concentration was measured by secondary ions mass spectroscopy. The electrical properties of the implanted 8-Ga2O3 epilayers were measured by transmission length method and Hall measurements. The sheet resistivity for the 8-Ga2O3epilayers with Si-ion dose of 1 x 1014, 6 x 1014 and 1 x 1015 cm-2 were found as 2.047, 0.158 and 0.144 Cd cm, respectively measured by Hall measurements and the electron carrier concentrations for the above doses were 4.39 x 1018, 6.86 x 1018 and 7.98 x 1019 cm-3. From the above results, the ion implantation was demonstrated to effectively reduce the resistivity with the high carrier concentrations.
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| 38. |
- Hossein-Babaei, Faramarz, et al.
(författare)
-
Growing continuous zinc oxide layers with reproducible nanostructures on the seeded alumina substrates using spray pyrolysis
- 2020
-
Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 46:7, s. 8567-8574
-
Tidskriftsartikel (refereegranskat)abstract
- The growth of zinc oxide thin films with controlled nanostructures on the heat resistant dielectric substrates is important for the fabrication of gas sensors, transparent electric heating elements, pyroelectric electron emitters, and many other potential electronic and optoelectronic applications. The preferred substrate for many of these applications is alumina, but the production of uniform ZnO layers on alumina is hindered by the large lattice mismatch between ZnO and Al2O3 hexagonal crystal structures. Here, we systematically investigate the growth process of ZnO thin films on alumina substrates using the ultrasonic spray pyrolysis (USP) of zinc chloride solutions in ethanol and, for the first time, demonstrate the deposition of uniform layers on the alumina substrates appropriately seeded using magnetron sputtering prior to USP. On the pristine substrates, random nucleation of the isolated nanocrystallites results in uneven layers, and extending the growth process leads to the hierarchical growth of facetted ZnO nanorods and pyramids with weak physical attachments to the substrate surface. In similar conditions, USP deposition on the seeded substrates reproducibly results in continuous networks of densely packed ZnO crystallites intimately attached to the substrate surface with adjustable thickness and electrical conductance. These results are compared with those obtained for SnO2 in similar conditions. Regardless of its tetragonal crystal structure, SnO2 reproducibly forms even layers on the pristine alumina substrates.
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| 39. |
- Hu, Qi, et al.
(författare)
-
Temperature stable dielectric properties of Mg2TiO4-MgTiO3-CaTiO3 ceramics over a wide temperature range
- 2023
-
Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 49:2, s. 1997-2006
-
Tidskriftsartikel (refereegranskat)abstract
- The zero resonant frequency temperature coefficient (zf) of microwave dielectric ceramics (MWDCs) at high and low temperature have attracted great attention in the development of microwave communication equipment. In this work, the Mg2TiO4-MgTiO3-CaTiO3 (MMC) ceramics with meeting the application requirements of 5G communication were prepared by traditional solid-phase sintering after investigating the relationship among phase compositions of xMg2TiO4-(0.931-x)MgTiO3-0.069CaTiO3 and 0.34Mg2TiO4-0.591MgTiO3-yCaTiO3, sin-tering process, and dielectric properties in detail. The results show that the dielectric properties of MMC ceramics are strongly affected by the phase relative contents of MgTiO3, Mg2TiO4 and CaTiO3. For instance, MMC ceramics with approximate zf = 0 is contributed by mutual compensation of Mg2TiO4 and MgTiO3, in which the Mg2TiO4 phase plays an important role in decreasing the zf value; and the increase of CaTiO3 will greatly increase the epsilon r value for MMC ceramics, while has a negative effect in the Q x f value. After three-phase regulation, the 0.32Mg2TiO4-0.611MgTiO3-0.069CaTiO3 microwave dielectric ceramic has a better dielectric temperature sta-bility, associated with dielectric properties of er = 19.7, Q x f = 55,400 GHz (at 8.43 GHz), zf-= 4.5 ppm/degrees C (-40 degrees C-25 degrees C), and zf+ =-5.1 ppm/degrees C (25 degrees C-90 degrees C).
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| 40. |
- Hussain, Fida, et al.
(författare)
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Comparative electrochemical investigation of zinc based nano-composite anode materials for solid oxide fuel cell
- 2019
-
Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 45:1, s. 1077-1083
-
Tidskriftsartikel (refereegranskat)abstract
- The structural and electrochemical properties of zinc based nano-composites anode materials with a composition of X0.25Ti0.5Zn0.70 (where X = Cu, Mn, Ag) have been investigated in this present study. The proposed Xo.zsTiousZno.70 oxide materials have been synthesized through sol-gel method. The doping effect of Cu, Mn, and Ag on TiZn oxides were analyzed in terms of electronic conduction and power density in hydrogen atmosphere at comparatively low temperature in the range of 650 degrees C. The crystal structure and surface morphology were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis techniques. The XRD patterns of composites depict that the average crystalline sizes lie in the range of 20-100 nm. Four -probe DC conductivity technique was used to measure the conductivity of the materials and maximum electrical conductivity of Ag0.25Ti0.05Zn0.70 oxide was found to be 7.81 S/cm at 650 degrees C. The band gap and absorption spectra were determined by ultra-violet visible (UV-Vis) and Fourier Transform Infrared spectroscopy (FTIR) techniques respectively. The maximum power density was achieved to be 354 mW/cm(2) at 650 degrees C by Ag0.25Ti0.05Zn0.70 oxide anode with SDC (electrolyte) and BSCF (conventional cathode) materials.
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| 41. |
- Imran, Z., et al.
(författare)
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Excellent humidity sensing properties of cadmium titanate nanofibers
- 2013
-
Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 39:1, s. 457-462
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Tidskriftsartikel (refereegranskat)abstract
- We report humidity sensing characteristics of CdTiO3 nanofibers prepared by electrospinning. The nanofibers were porous having an average diameter and length of similar to 50-200 nm and similar to 100 mu m, respectively. The nanofiber humidity sensor was fabricated by defining aluminum electrodes using photolithography on top of the nanofibers deposited on glass substrate. The performance of the CdTiO3 nanofiber humidity sensor was evaluated by AC electrical characterization from 40% to 90% relative humidity at 25 degrees C. The frequency of the AC signal was varied from 10(-1) to 10(6) Hz. Fast response time and recovery time of 4 s and 6 s were observed, respectively. The sensor was highly sensitive and exhibited a reversible response with small hysteresis of less than 7%. Long term stability of the sensor was confirmed during 30 day test. The excellent sensing characteristics prove that the CdTiO3 nanofibers are potential candidate for use in high performance humidity sensors.
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| 42. |
- Imran, Z, et al.
(författare)
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Fabrication of cadmium titanate nanofibers via electrospinning technique
- 2012
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 38:4, s. 3361-3365
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Tidskriftsartikel (refereegranskat)abstract
- Here we present an electrospinning technique for the fabrication of cadmium titanate/polyvinyl-pyrrolidone composite nanofibers. The composite nanofibers are then annealed at 600 degrees C to obtain ilmenite rhombohedral phase cadmium titanate nanofibers. The structure, composition, thermal stability and optical properties of as synthesized and annealed cadmium titanate nanofibers are characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy and ultraviolet-visible spectroscopy. The average diameter and length of the nanofibers are found to be similar to 150-200 nm and similar to 100 mu m, respectively.
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| 43. |
- Irshad, Muneeb, et al.
(författare)
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Evaluation of densification effects on the properties of 8 mol % yttria stabilized zirconia electrolyte synthesized by cost effective coprecipitation route
- 2021
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Ingår i: Ceramics International. - : ELSEVIER SCI LTD. - 0272-8842 .- 1873-3956. ; 47:2, s. 2857-2863
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Tidskriftsartikel (refereegranskat)abstract
- In the current work, properties of 8YSZ powder synthesized by co-precipitation method and sintered at 1200 degrees C, 1300 degrees C and 1400 degrees C are investigated. XRD analysis shows that all 8YSZ samples exhibit cubic phase and increased crystallite size is observed with increased sintering temperature. The relative density measurements show increased densification due to increased sintering temperature and relative density >96% is obtained for 8YSZ sintered at 1400 degrees C. SEM micrographs also confirm that structure becomes denser with increase in sintering temperature. EDX analysis confirms the elemental composition of 8YSZ and no impurity is observed while thermal analysis reveals weight losses within different temperature ranges. High ionic conductivity and maximum power density of 0.41 Wcm(-2) is obtained for cell having 8YSZ electrolyte sintered at 1400 degrees C owing to its compact, dense and gas tight microstructure.
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| 44. |
- Islavath, N., et al.
(författare)
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Spray coated seed layer for scalable synthesis of aligned ZnO nanowire arrays on FTO substrate and their photovoltaic properties
- 2015
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Ingår i: Ceramics International. - : Elsevier Ltd. - 0272-8842 .- 1873-3956. ; 41:3, s. 4118-4122
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Tidskriftsartikel (refereegranskat)abstract
- Spray coating has been employed as a non-vacuum route for deposition of a ZnO seed layer on large-area fluorine-doped tin oxide (FTO) glass substrates. Optimization of spray parameters, particularly precursor flow rate and volume, was found to yield preferably oriented and uniform ZnO seed layer. Vertically aligned single crystalline ZnO nanowire arrays with controlled features were grown on aforementioned substrate at 95 °C by a hydrothermal method. The current-voltage characteristics of dye-sensitized solar cells fabricated with the aligned ZnO nanowire arrays as photoanode have demonstrated a maximum photocurrent density of 1.86 mA cm-2 under 1 sun illumination (100 mW cm-2, AM 1.5G). © 2014 Elsevier Ltd and Techna Group S.r.l.
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| 45. |
- Israr Qadir, Muhammad, et al.
(författare)
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Fabrication of ZnO nanodisks from structural transformation of ZnO nanorods through natural oxidation and their emission characteristics
- 2014
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 40:1, s. 2435-2439
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Tidskriftsartikel (refereegranskat)abstract
- An environmentally benign natural oxidation based synthetic technique has been developed to grow and transform the ZnO nanorods into nanodisks at a very mild temperature of 55 degrees C with excellent features of its novelty and reproducibility. Metallic zinc foil and formamide solution have been utilized as substrate and reacting solution, respectively, for the growth of ZnO nanostructures. The optimized values of temperature, concentration of formamide and the reaction time are achieved to obtain the controlled and desired nanoscale morphologies. Detailed mechanism of the structural transformation of the nanorods into nanodisks has been discussed. Strong ultraviolet emission peak along with the much weaker deep level defects related emission has been realized in the microphotoluminescence spectrum. A visible red-shift and decrease in the intensity of ultraviolet peak are observed with increasing range of temperature from 20 to 300 K.
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| 46. |
- Jamil, Hira, et al.
(författare)
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Electrospun titanium dioxide nanofiber humidity sensors with high sensitivity
- 2012
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 38:3, s. 2437-2441
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Tidskriftsartikel (refereegranskat)abstract
- Titanium dioxide nanofibers were synthesized using electrospinning technique. The nanofibers were porous with an average diameter and length of similar to 150 nm and 200 p,m, respectively. Humidity-sensing devices were fabricated by lithographically defined aluminum electrodes on top of the nanofibers deposited on silicon dioxide grown thermally on a silicon substrate. The performance of a TiO2 nanofiber humidity sensor was tested by AC and DC electrical measurements at 40-90% relative humidity. The response and the recovery time were 1 s and 4 s, respectively, between 40% and 90% relative humidity. The sensitivity of the TiO2 humidity sensor in the range of 40-90% RH was 150 M Omega/%RH and 20 M Omega/%RH at 10 Hz and 100 Hz, respectively. The excellent sensing characteristics are attributed to the porous nature and the small diameter of the nanofibers.
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| 47. |
- Jamil-Rana, Sadaf, et al.
(författare)
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Naturally oxidized synthesis of ZnO dahlia-flower nanoarchitecture
- 2014
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 40:8, s. 13667-13671
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Tidskriftsartikel (refereegranskat)abstract
- Three dimensional ZnO dahlia-flowers have been engineered at room temperature relying on natural oxidation based aqueous chemical synthetic approach. Glycine abetted multicomponent isotropic morphology has been synthesized through the conglomeration of thin nanopetals as building blocks with highly large surface area to volume ratio. Highly controllable morphology of thin nanopetals is achieved by stabilizing their polar faces through the adsorption of reactive hydroxyl and amide functions of glycine. Fourier transform infrared conclusions also exemplify good corroboration towards the use of organic additives. Moreover, the synthesized ZnO flowers have been utilized to fabricate cholesterol biosensor and biosensing measurements which have been performed over the cholesterol concentration range of 1 x 10(-6) M to 1 x 10(-3) M.
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| 48. |
- Jiang, Zhiwu, et al.
(författare)
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In Situ Fabrication and Properties of 0.4MoB-0.1SiC-xMoSi2 Composites by Self-propagating Synthesis and Hot-press sintering
- 2018
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 44:1, s. 51-56
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Tidskriftsartikel (refereegranskat)abstract
- Mo, Si and B4C powders were used to fabricate 0.4MoB-0.1SiC-xMoSi2 composites by self-propagating high-temperature synthesis (SHS) and hot pressing (HP). The effects of MoSi2 content (x=1, 0.75, 0.5 and 0.25) on phase composition, microstructure and properties of the composites were investigated. The results showed that the 0.4MoB-0.1SiC-xMoSi2 composite exhibited Vickers hardness of 10.7–15.2 GPa, bending strength of 337–827 MPa and fracture toughness of 4.9–7.0 MPa∙m1/2. The fracture toughness increased with the increasing volume fraction of MoB and SiC particles which were promoted by the toughening mechanisms, such as crack bridging, cracks deflection and crack branching. Moreover, the electrical resistivity showed an increasing trend with decreasing volume fraction of MoSi2.
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| 49. |
- Jurków, Dominik, et al.
(författare)
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Investigation of High Temperature Co-fired Ceramic tapes lamination conditions
- 2015
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Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 41:6, s. 7860-7871
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Tidskriftsartikel (refereegranskat)abstract
- The main goal of this paper was to analyze the influence of lamination process conditions and High Temperature Co-fired Ceramic (HTCC) tape composition on the lamination quality (existence of delaminations). The second aim was to estimate the influence of lamination conditions and HTCC tape composition on three process outputs: compressibility, surface roughness and density of High Temperature Co-fired Ceramics and to recognize if these outputs can be useful from lamination quality investigation point of view. The bonding quality was investigated using scanning acoustic microscopy (SAM). The analyzed ceramics was fabricated using water based slurries in the frame of tape casting process. The paper additionally discusses limitations and drawbacks of the used investigation methods and experiment design.
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| 50. |
- Jurkow, Dominik, et al.
(författare)
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Investigation of High Temperature Co-fired Ceramics sintering conditions using Taguchi Design of the experiment
- 2014
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Ingår i: Ceramics International. - : Elsevier Ltd. - 0272-8842 .- 1873-3956. ; 40:7 PART B, s. 10447-10455
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Tidskriftsartikel (refereegranskat)abstract
- Influence of sintering conditions of High Temperature Co-fired Ceramics on surface roughness, density and shrinkage of the sintered samples is presented in this paper. The investigations were conducted using Taguchi Design of the experiment. Mathematical statistics was applied in the estimation of the optimal process conditions. The estimation accuracy was verified by real measurements.
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